The present invention relates to a method of removing a charge from an electrophotographic photoreceptor provided with surface insulation.
Conventionally, of a variety of electrophotographic photoreceptors provided with layers of surface insulation, the typical photoreceptors have triple layers comprised of the conductive layer, photoreceptive layer, and the insulation layer, respectively. Generally, the triple-layer photoreceptor is provided with satisfactory characteristics featuring high sensitivity and sharp contrast. In particular, the triple-layer photoreceptor provided with a photoreceptive layer comprised of cadmium sulfate dispersed into an organic binder has been widely used because of its high sensitivity and economy. Nevertheless, the photoreceptor still poses problems related to "compatible characteristics with darkness." This refers to the specific characteristics significantly noticeable in conventional triple-layer photoreceptors. The characteristics of these photoreceptors significantly vary when the photoreceptors are stored in a dark location for a long time. One of the critical problems caused by said "characteristics compatible with darkness" is the significantly variable concentration of developed pictures through successive use of a triple-layer photoreceptor after a certain storage period. This symptom is caused by variations in the static capacitance of the photoreceptor layer itself as the result of a gradual release of charges from the photoreceptive layer during the storage period. To solve this problem, some prior art devices attempted to minimize the picture concentration variations by applying "charge-removing" light. This was done by applying an electric field to the photoreceptor immediately before the picture formation process begins. Nevertheless, even after applying a large amount of "charge-removing" light, the concentration of the first picture that was developed using photoreceptors that were idle for a long time turned out to be significantly weak. Conversely, the picture concentration tended to increase during the continuous electrophotographic copying that followed. Conversely, when the amount of charge-removing light was too small, concentration significantly varied between the first and second pictures developed when photoreceptors once subjected to said "characteristics compatible with darkness" were used. Yet the picture image could be poorly developed. As a result, it was extremely difficult for conventional techniques to detect the optimum amount of light due to the different characteristics of each photoreceptor.